Measurement of Color Constancy by Color Memory Matching

Degree of color constancy was measured when color memory was involved in color comparison judgment. We used the Optical Society of America (OSA) Uniform Color Scales as stimulus color samples, and chose 20 color samples as test stimuli. Four illuminants of 1700, 3000, 6500, and 30, 000 K were tested. The observer, completely adapted to a test illuminant, saw a test color sample and stored its color in his memory. After being readapted to the reference white (6500 K), he started selecting a color sample from among the 424 OSA samples which matched the test sample in his memory. We employed a memory matching method called cascade color matching, in which the number of selected color-samples was gradually reduced in four stages. In the final stage, the observer selected a color sample. The results show that, for most test colors, the distributions of selected colors in stages 1 to 4 were similar among all illuminants, and that the u’v’ chromaticity distance between a test color under 6500 K and its matched color was quite short. These indicate that good color constancy was retained in memory color comparison.     

基于线性数据库的色差权重因子计算机配色

计算机配色广泛应用于纺织印染、涂料油漆、塑料、建材等工业领域。计算机配色的基础理论是库贝尔卡-芒克(Kubelka-Munk)函数与浓度的线性关系,但实际上,库贝尔卡-芒克函数与浓度呈非线性关系,这限制了计算机配色在我国的广泛应用,为此,提出一种数学方法,建立一个线性染料数据库。全光谱配色方法是计算机配色的重要方法之一,但对物体而言,每个波长上同等光谱反射率的变化却显示出不同程度的颜色感知差异,在某些波长处,呈现较强的灵敏性,而在另外一些波长处有较大的惰性,因此,根据色度学理论,为全光谱配色提供每个波长处灵敏程度不同的色差型权重因子。同时,为色差权重因子提供线性染料数据库。结果证明,数据库的线性程度明显提高,使用色差权重因子配色的效果明显提高。     

颜色视觉匹配中显示器颜色色差阈值的评价

为了对阴极射线管(Cathode ray tube,CRT)显示器颜色恰可辨别的小色差阈值进行评价,在中性灰背景下,用编制的颜色匹配程序,在CRT显示器上随机产生颜色,分别调节程序中R、G、B通道的值,使匹配色与随机色达到视觉上的一致,进行颜色视觉匹配实验,测量CRT显示器上随机色和匹配色的L*a*b*值.用不同的色差公式对实验数据分别从明度、色调、饱和度进行比较分析,色差公式评价小色差的性能是CIEDE2000优于CMC(2∶1)和CIEL*a*b*.在a*b*图上绘制实验颜色恰可辨别图.不同色差公式计算的CRT显示器恰可辨别小色差阈值不同.     

Colorimetric Calibration of Video Cameras Using Two Color Constancy Models

Colorimetric calibration of color imaging devices is important to realize device independent color reproductions. However the calibration for digital or video cameras is difficult because a color image is acquired for unknown objects under various unknown illuminants. An experiment was carried out based on two computational color constancy models, the finite-dimensional linear model and the spectral sharpening model, to estimate colorimetric values using image data of a color chart captured by video camera. We estimated the colorimetric values by using a single reference reflectance with known spectral reflectance in a color chart under an unknown illuminant. The accuracy was evaluated by color differences in CIELAB color space and was compared on three different color charts under three different illuminants including a fluorescent lamp. It was confirmed that the two computational models do not require prior knowledge of illuminants and surfaces. The finite-dimensional linear model gave more accurate results than the spectral sharpening model in the simulations and experiments.     

Color Property of the Recognized Visual Space of Illumination Controlled by Interior Color as the Initial Visual Information

It was shown that the color property of the recognized visual space of illumination, RVSI was controlled by changing the initial visual information by arranging objects in the room all shifting toward orange direction. We constructed two miniature rooms, D and I, both illuminated by the same daylight type fluorescent lamps but arranged with furniture of different color, those in room I shifting toward color as if they were illuminated by an incandescent lamp. Subjects felt as if room I were illuminated by an incandescent lamp. A test patch was placed midair in each room and its color was judged. When the test patches were placed in room I their colors were all perceived to be shifted toward greenish blue compared to those of test patches placed in room D, in spite of having the same illumination. The results imply that the apparent color of an object is determined not by its chromaticity, but in relation to the color property of the RVSI of the room where the object is observed.     

Color Modification of Pictures Requiring Same Color Impression as Real Scene

Color constancy is an important feature of the human visual system. Our visual system adapts almost instantly to new illumination and we can perceive the color of objects in a new space correctly whatever color the illumination may be. This feature is not solely that of a commercially available camera. The difference between the human visual system and a camera raises a problem in our observation of pictures. We cannot see the exact color that a photographer intended to show us through a picture. Some color modification must be made to the picture to resolve this. In the present paper, the degree of modification was determined for various color combinations of illumination for taking a picture, FL_L and observing the picture, FL_o. An entire experiment was carried out in an actual room based on the belief that color appearance of objects is determined in relation to the recognized visual space of illumination (RVSI). A subject observed the color of a room lit by FL_L and pictures of the room lit by various colors of FL_L were taken. The pictures were displayed in another room lit by FL_o and the subject chose the picture that gave him/her the same color impression as the room of FL_L. In the case of picture slide, the color of the picture must be modified as if it were taken with the illumination inbetween the color of FL_L and FL_o. In the case of picture print, a similar modification was needed for reddish FL_L and white FL_O, but it was not needed for white FL_L and reddish FL_o.     

Color Appearance Explained,Predicted and Confirmed by the Concept of Recognized Visual Space of Illumination

Ten years have passed since we proposed a new concept called recognized visual space of illumination (RVSI). The central idea of the concept assumes that our brain first recognizes how a space is illuminated and then judges colors of anything seen in the space in relation to the RVSI constructed for the space. In another expression we say that the space is recognized first and the color perception next. In this paper some of our experiments that proved the appropriateness of the concept will be introduced. When a white paper was seen through a colored filter we could perceive the paper as white at the same instant we recognized a space through and beyond the filter. When an achromatic patch independent from the room illumination was observed under colored illumination its appearance immediately changed to that roughly opponent to the illumination color. When two gray patches of the same lightness were drawn in a picture of a white grating on a black background on a way that one appeared to locate on this side of the grating and the other in the other side, the former appeared brighter. These all confirmed the predictions based on the RVSI concept.     

Color appearance seen through a colored filter of various sizes

It will provide us an effective method to study the color perception of the elderly if we can employ for young subjects a pair of glasses with color property chosen to simulate that of the elderly. One problem has to be solved before using such glasses based on the concept of the recognized visual space of illumination, that is, the size of the glasses. When a piece of a white paper is seen through a yellow filter in a room, it naturally appears yellowish. But if the observer uses the filter to cover his/her eyes entirely the white paper returns to its original white; this is known as color constancy. Between these two extreme cases, the color is expected to change from yellow to white. Chromaticness and hue of an achromatic test chart of a small or large size were determined by the elementary color naming method when the chart was seen monocularly through a red, yellow, green or blue filter, respectively, placed at various distances from the eyes. Chromaticness was large at around 40% when the visual field through the filter was equal to or smaller than the test chart, but it rapidly decreased when the visual field extended over the test chart so that objects other than the test chart were included in the visual field. It decreased to almost zero when the filter was about 5 cm or less away from the eye. It was concluded that we do not necessarily have to use goggles to cover the entire visual field but can use a normal pair of glasses made of colored filters for young subjects to study the color perception of the elderly with understanding that the study is only for the color perception experienced while wearing the glasses.     

颜色视觉匹配中明度阈值的评价

为了对颜色视觉匹配中的明度阈值特性进行评价,采用在阴极射线管显示器上获得的颜色刺激,在5个不同明度的中性色背景下,标准刺激的明度L*从5到95以5个CIELAB单位为变化步长,共对19个不同明度的中性标准颜色进行视觉匹配实验。通过对实验结果的处理和分析,验证了关于颜色刺激视觉辨别明度阈值与背景明度之间相关性的韦伯法则和crispening效应,同时利用颜色视觉匹配数据对基于CIELAB的相关色差公式进行了评价和比较,CIEDE2000具有最好的明度差预测性能,CMC次之,CIELAB和CIE94最差。     

The Brain Adaptation to the Color of Illumination and not the Retinal Adaptation to the Color of Objects that Determines the Color Appearance of an Object in the Space

Color appearance was measured for a test patch which was placed in a test room illuminated by the daylight type of illumination and was looked at from the subject room illuminated by one of the four colored illuminations, red, yellow, green, and blue, through a window of three different sizes. When the window was the smallest so that only the test patch was seen within the window the color of the test patch appeared almost opponent to the illumination color, but as soon as something is seen within the window of larger size the color returned to the original color of the test patch to indicate the color constancy. To recognize the test room as a space was essential to perceive the real color of the test patch. This returning to the original colors was not influenced by green color of objects densely placed in the test room or by red color of objects again densely placed in the test room. The results imply that the color appearance of the test patch is not determined by the retinal chromatic adaptation, but by the brain adaptation to color of the illumination in the space.     

计算机自动配色预测算法研究

基于配色基础理论Ｋｕｂｅｌｋａ－Ｍｕｎｋ定律的常数形式，建立了计算机自动配色的三刺激值匹配算法，通过纺织印染自动配色预测实验表明该算法可获得色差ΔＥ小于０．１０ＣＩＥＬＡＢ的满意配方。     

Color Constancy in a Photograph Perceived as a Three-Dimensional Space

It is known that color constancy does not hold in a photograph. This could be because the photograph is recognized as a two-dimensional paper. Based on the concept of the recognized visual space of illumination (RVSI), it is predicted that color constancy holds in the photograph if it is perceived as a 3-D scene. We examined whether the color constancy held under a special viewing condition. A photograph of a room under incandescent illumination was shown under daylight illumination. We tested the neutral color perception of a stimulus on the photograph both with and without a dimension-up viewing box showing the photograph alone monocularly. The results showed good color constancy when a subject observed the photograph with the viewing box. It was also shown that the degree of color constancy decreased for a jumbled photograph without 3-D information. Our results suggest that the recognition of a space and illumination are important in color perception.     

Color Appearance Determined by Recognition of Space

The color appearance was measured for a test patch which was placed in a test room illuminated by daylight lamps and was looked at from a subject room illuminated by one of four colored illuminations, red, yellow, green and blue, through windows of various sizes. When the window was small so that only the test patch was seen within the window the color of the test patch appeared almost opponent to the illumination color, but as soon as something was seen within the window of a larger size the color returned to the original color of the test patch. To recognize the test room as a space was essential to perceive the real color of the test patch. The results were explained by the concept of the recognized visual space of illumination.     

基于CRT的非对称视觉匹配实验中对立色的显示方法研究

对立色是颜色科学研究中的一类特殊颜色现象,通过对其特殊匹配现象的研究,可以揭示人眼彩色视觉信息传递的规律。针对基于CRT的非对称视觉匹配实验的要求,提出了一种色调均匀分布、强度成线性变化的对立色的定义和显示方法,实现了人眼锥体细胞响应LMS与计算机彩色量化值RGB之间的高精度转换和真彩色再现。     

用于计算机配色的反射光谱数据质量评估方法研究

基础色样的反射光谱数据质量是影响计算机配色结果的重要因素之一。目前评价配色反射光谱数据质量的方法有反射光谱检测法和K/S检测法,但这两种方法需检测每种基础色样和各个波长的反射率与K/S值,检测过程过于复杂,故不适用于光谱数据质量的快速直观检测。本文使用45°/0°和d/8°几何条件的分光光度计测量以铜版纸和银卡纸为基材的胶印油墨基础色样反射光谱数据,基于光谱检测法优化获取基础色样反射光谱数据的几何条件,提出了一种明度色度对比检测法;并对比分析了反射光谱检测法,K/S检测法和明度色度对比检测法。结果表明,45°/0°和 d/8°几何条件均可用于铜版纸基础色样反射光谱数据的测量,但45°/0°几何条件不符合银卡纸基础色样反射光谱数据的测量要求;而对于d/8°分光光度计,在包含镜面反射时,银卡纸为基材的透明白反射率小于各基色墨反射率,且青墨与品红墨反射率分别在浓度为60%开始出现异常交叉,从而导致高浓度区域光谱质量较差;而在明度色度对比检测图中,青墨与品红墨样条与参考铜版纸基础数据偏离更加明显。故须选择大于或等于各基色墨反射率的透明白,基础色样中需约束青墨与品红墨的最大浓度;以漫反射特性较好的铜版纸作为配色基材时,明度色度对比检测法检测效果较现有两种检测法更为直观。     

基于非对称密码系统的彩色图像加密技术

为了实现对彩色图像的加密,提出一种基于傅里叶变换和非对称密钥加密系统的加密方法。把彩色图像分成三基色分量:红,绿,蓝。然后对这3帧灰度图像的傅里叶频谱进行截取,合成一个目标图像,该目标图像包含了原始彩色图像的大部分信息。对此目标图像的幅度和相位分别用非对称密钥加密系统加密,即实现了彩色图像的加密。 给出了理论分析和计算机模拟结果,实验结果证实了该方法的可行性。     

Stearns-Noechel模型的全光谱纱线配色算法

目前计算机配色中,拟合样与标准样的色差小时配方偏差较大,打样结果不理想,难以预测准确配方。在光学模型Stearns-Noechel模型的基础上进行算法优化。利用两个样品的分光反射率数据相等,则两个样品必然等色的特性,改进计算机配色算法程序中的判别条件,即通过MATLB编程计算,在区间[0 1]中,每间隔0.001,循环未知参数M值,选择全光谱反射率数据偏差最小时的参数M值计算拟合配比,代替色差最小时的参数M值计算拟合配比,并分别计算拟合样与标准样的相对配方偏差进行对比。结果表明,选择全光谱反射率数据偏差最小时参数M值对应的拟合配方,一次色的平均配方相对偏差为0.560,二次色为0.346;选择色差最小时参数M值对应的拟合配方,一次色的平均配方相对偏差为0.723,二次色为0.383;两种方法对比,可以看出无论是一次色还是二次色,优化算法后拟合样品与标准样品的配方相对偏差都比选择色差最小时对应的的相对配方偏差小,即优化后的拟合配方更加接近真实配方,配色精确度得到明显提高,有利于减少后期打样次数,提高配色效率。     

基于Land实验的可见红外伪彩色图像融合方法

由Land在研究人类视觉颜色恒定性现象时从所做的某个实验出发,通过对该实验中所用红、绿色滤波片的理想化假设以及光源的等能分布假设,并建立红外图像与红色透明片、可见光图像与绿色透明片的对应关系,得到Land实验启发下的新的伪彩色融合算法。通过与Toet伪彩色融合算法的结果比较,说明了该方法的有效性。进而借鉴Toet算法中强调图像特有成分的思想,使本算法输出更丰富、更逼近真实景物的色彩。     

平均场动力学与冷密夸克物质色导率

首先介绍了非Abel输运理论基础,然后在经典非Abel输运理论的基础上引入并评述了平均场动力学.作为应用,研究了有限化学势下冷密夸克物质系统的色动力学并计算出了色导率.最后比较了有限温度和有限化学势下的结果,讨论了其在天体物理领域的潜在价值.     

彩色计算全息颜色匹配的研究

基于色度学原理,研究了彩色计算全息颜色的匹配问题,给出了电子显示色系下颜色量与计算全息物光波振幅之间的等色传递关系.首先,讨论了电子显示色系和彩色计算全息色系之间的颜色传递问题,并且给出了这两个色系下颜色量的转换方法.其次,以彩色全息再现像与原始计算目标颜色一致为目的,分析了彩色计算全息色系下的颜色量和与其对应物光波振幅的关系,并得出了颜色量和物光波振幅间应满足的一般方程.最后,本文选取PAL制式彩色显示色系下的彩色目标为全息图计算物体进行了彩色全息显示实验,结果表明本文所述彩色计算全息颜色匹配方法是有效的.本文的研究工作将为彩色计算全息显示的实用化奠定一定的理论基础和技术依据.